It's easier to have your parents use a mac.
It's much cheaper to give your parents your old PC or laptop with an updated distro (say, Ubuntu) and forget about viruses, etc. They usually get most of their needs from the web (eg. webmail, facebook, etc.) and you can SSH in the event they actually need to install anything.
If you are a developer, it's very likely your old PC or laptop will be good enough for their needs.
It's also much more useful as a teaching tool. Instead of whatever the problem was being silently fixed behind the scenes... then cropping right back up again because it's caused by user error, your client can follow along and actually learn something.
That's my favourite thing about ARD. I can curtain a machine if I don't want questions or interruption, and I can reveal it if I want to teach something.